We study the microstructure and growth mechanism of copper (Cu) ramified aggregates by the optical microscopy and atomic force microscopy. We find that the ramified Cu aggregates exhibit a granular structure with mean size of the single particulate in the range of 30-60 nm. It is interesting that the average width of the ramified aggregates and the mean size of the particulates do not change obviously with the increase of the nominal film thickness. Compared the size distributions of the Cu particulates on the oil surfaces with that of Cu films on glass surfaces, we suggest that the surface morphology and microstructures of Cu aggregates (or films) depend on property of substrates. The interpretation for this phenomenon is also presented. (C) 2009 Elsevier B.V. All rights reserved.